Yumeshiro enters the Shin'o Academy and quickly establishes himself as a top student. He's good at everything he gets his hands on. Anyone who trains with him is made better by it. He's the talk of both students and teachers, and that's when he first hears the name "Hideyori." It'd been centuries since Hideyori Yamamoto was a student at the academy, but he was still on the instructors' minds, in that Yumeshiro was a genuine contender for the top spot, since he made almost as good of an impression as Hideyori, who was also known for being the top of his class in everything. For the first time in his life, Yumeshiro is being compared to someone and that other person keeps coming out on top. He decides he has to make a better impression. Hideyori becomes his rival. 

Yumeshiro finds out as much as he can about Hideyori, how he was top of his class every year yet didn't graduate early ('He must've done it on purpose,' Yumeshiro thought), and that his closest friend was another top contender, but before that, it was a noble from one of the four houses ('Good riddance,' came Yumeshiro's grimace), and then there's the fact that he's the son of the Captain Commander, yet you wouldn't know it since Yamamoto never showed any favouritism ('Then he's worthless as a father,' Yumeshiro thought bitterly).

Little does he know, Tadakatsu is presently being tutored by Hideyori, and when Tadakatsu puts two and two together and figures out that his Hideyori and Yumeshiro's Hideyori are the same, he decides to keep it to himself, planning on making a fool out of Yumeshiro one day, especially since he knew the man Yumeshiro envisioned was a tall, menacing, chiseled man, when Hideyori is anything but that. It's hilarious to Tadakatsu. He eagerly awaits the day they meet.

After Yumeshiro's graduation, he joins the Sixth Division and becomes quite notorious for his immense strength and talent, and Captain Kuchiki's favouritism, as well as being seated upon graduation. Talk of the Oni of the Sixth Division attracts Hideyori, and after he spends time keeping a close eye on Yumeshiro, he approaches the man on a day where he's surrounded by his teammates, and introduces himself as Hideyori Matsunaga. He's in the First Division, and carries himself with reserved grace, the kind of man that Yumeshiro would respect if not for his overtly feminine charms. Ugh, this is the worst. 

Though Hideyori makes note of how the usually belligerent Yumeshiro is more warmly receptive to him, their conversation is not as friendly as he would've liked. He tries again on another day, and this time, almost manages to convince Yumeshiro to go to the First Division hot springs with him, before Yumeshiro becomes privy to his plans and puts a stop to it. Slowly but surely, they work up to a sort of friendship, though Yumeshiro still holds Hideyori at a distance. He's still not sure what to make of the other man. There's something untrustworthy about him. Once he's solidified himself in Yumeshiro's life, Hideyori decides to get advice on how best to proceed from one of his dearest friends.

Hideyori asks Tadakatsu if he's heard of Yumeshiro Hatada, and that's when Tadakatsu can't take it anymore. Of course he knows "Shiro-chan," that's his best friend! How two men can independently come to ask about each other is beyond hilarious! 

Tadakatsu introduces the two formally. The punch he gets from Yumeshiro is so worth it. 

It's not long after that Hideyori tells Yumeshiro of his future plans, how he wants to be Captain Commander, and how his father is standing in his way. Yumeshiro's response is immediate. "Then kill him. I never liked that old bastard anyways." Hideyori is not as taken aback as he should be. Yumeshiro knew something was off. "I'll help you do it, if you'll let me." 

That surprises Hideyori, pleasantly so. The fire in Yumeshiro's eyes is intense and cold. He makes it sound so easy, and part of Hideyori knows it would be. for the two of them, that is. He just has to make sure. "You will?" 

Yumeshiro nods. Such ambition, the kind that will change the very nature of their society; that is the kind he will see to fruition. This is a man he will follow into hell. "Yes, I'll make you Captain Commander. Just give me an order and I'll do it."

At long last, Hideyori's found someone to stand by him no matter what.

Sōsuke Aizen revealed his nefarious plot at the Sōkyoku Hill, that he was betraying Soul Society for a higher purpose, to become something greater than the Soul King himself. Yumeshiro always had a feeling about the Fifth Division Captain. He was off, hiding something, though Yumeshiro could never read him. It didn't matter to Yumeshiro, who had no relationship with Aizen. Aizen's betrayal meant another punishment to be dished out, but what shattered Yumeshiro entirely was that Hideyori went with Aizen. 

Tadakatsu refused to believe it, and at first, Yumeshiro did too, but then came those doubts, doubts that were always associated with Hideyori in relation to his standing with Aizen. Yumeshiro couldn't help but feel like second best, the consolation prize, the short end of the stick. It was only natural that Hideyori go with the man that promised him eternity, so why did it hurt so damn much? Maybe because Hideyori's greatest fear was betrayal, and going with Aizen meant Yumeshiro had to accept Hideyori's betrayal too. His expectations were far from reality. 

The only way he knew to reconcile these doubts was to hide them, and hide them he did. Buried them way down deep. It was already decided. Yumeshiro's blade was not reserved for such disgrace, he would not serve someone so treacherous.

But then Tadakatsu approaches Yumeshiro with a direct order from the Captain Commander, to retrieve Hideyori from Hueco Mundo while the divisions steal Aizen's attention away to a fake Karakura Town. Tadakatsu is excited to have a mission from the head honcho, but Yumeshiro is wary. Anyone could've done this, and the old man chooses Katsu? Yeah right. 

He should've trusted his gut. The minute they step foot in Hueco Mundo, things are off to a bad start with the arrival of Ryoma Utsubayashi, a shinigami who'd been banished from Soul Society and claimed he was an old friend of Hideyori's, who came to help free his estranged companion. Strange, since Hideyori never mentioned him, and neither did the rest of the First Division. The squad's idiot leader decides to trust Ryoma. Yumeshiro doesn't like it one bit, and keeps Ryoma under a watchful eye and at an arm's length. 

When the group arrives at Las Noches, they split off. Mutsuki goes west with Ryuuhime, and Tadakatsu and Yumeshiro go east. Ryoma goes off on his own. Tadakatsu and Yumeshiro come across Dante Decimus, an arrancar with Hideyori's zanpakutō in hand. 

Assuming the worst, they engage in combat with the arrancar, though something he says during the battle sets Yumeshiro off. How dare he claim to be closest to Hideyori? How dare he call himself Hideyori's friend? He's delusional, an abomination, nothing more than a soldier in Aizen's army! If Hideyori really was that close to this bastard, then it was confirmation enough. Hideyori knew of Aizen's plans all along. He was always involved, and nothing between them was true. Not even his ambition to become Captain Commander. 

When they defeat the arrancar and find their way to Hideyori, they're half dead, but Hideyori's only concern is with Dante, who he demands to go see. His sobs are immeasurable, his Reiatsu goes wild, and the only person who can calm him down is Tadakatsu. Then Hideyori wants to go to the fake Karakura Town to see Aizen. All of this is singed into Yumeshiro's memory, the fact that Hideyori was one of them. Yumeshiro is cruel to Hideyori, treating him like he would any traitor or criminal. 

Yet this all becomes irrelevant when the group arrives at Karakura Town and Yamamoto orders Hideyori to hand over his blade under arrest. Tadakatsu is immediately prepared to fight despite his condition, as is Yumeshiro. That's when Ryoma shows his hand and reveals himself as a traitor who'd been given orders by Yamamoto to suppress the group before they could start an unnecessary fight. If any harm befell a noble such as himself, they'd all be subject to execution, so they were forced to stand back as Hideyori was unfairly defeated by Ryoma and taken in restraints. Yumeshiro would never forgive Mutsuki for holding him back the way he did, nor would he forgive Yamamoto and Ryoma. But most of all, he'd never forgive himself for his weakness.

After Hideyori is imprisoned, Yumeshiro is aimless once again, and that aimlessness turns to belligerence. He's angry, volatile, and doesn't follow orders. He's drunk quite frequently, because what's the point of upholding his perfect image when everyone saw his weakness and failure? He couldn't muster the strength to fight for his master, he couldn't even break free of Mutsuki's hold. Filled with regret and guilt. He's shameful. He's disgusting. He's nothing.

Captain Kuchiki sees how fraught with despair his Sixth Seat is, and he orders Yumeshiro to take a break and return at full capacity, but Yumeshiro refuses, forcing Byakuya's hand into writing him up for a suspension until further notice. Yumeshiro's drinking gets worse after that. He goes back to Despair Mountain, and goes back to being the Oni, lonely and desolate.

When Hideyori is released two years later due to a noble's meddling, Tadakatsu holds a village-wide welcome party in Aosen Town. Yumeshiro is distant. Hideyori can barely get a word with him, that is, until Yumeshiro needs to go outside for some air. Seizing the opportunity, Hideyori follows him outside to sit with him, and there they air out their thoughts.

Yumeshiro doesn't apologize. Hideyori didn't expect him to, but he got something that was close. Yumeshiro admitted he was wrong. He gets on his knees, bows his head to the floor, and begs Hideyori for forgiveness, swearing upon his life that he will never again doubt Hideyori's intentions, and will serve without question from now on, solidifying their oath. Hideyori accepts this, but then kneels to Yumeshiro's level, and warns him gravely of the consequences to doubting him in the future. With that, their relationship is patched up, and they return to the party with newfound vigour. 

Soon after that, Yumeshiro returns to the Sixth, and not only is he reinstated, but he is promoted to Third Seat. Hideyori is accepted back into the First Division and given Ryoma's old seat.

Notes:
- Sankeihana really likes Oniseigi :Y

Notes: